The objective of the proposed research is to elucidate some of the mechanisms for the control and regulation of specific DNA-directed RNA transcription from the chloroplast chromosome of Euglena gracilis. This genome can undergo a developmental transition during light induced chloroplast development where there are temporal changes in RNA synthesis. The aim is to experimentally determine changes in RNA synthesis in vivo, and to correlate such changes with components of the transcription apparatus in a purified in vitro system. Studies on in vitro transcription utilized a purified, transcriptionally active chromosome isolated directly from Euglena chloroplasts that selectively transcribes the chloroplast DNA. BIBLIOGRAPHIC REFERENCES: Barry K. Chelm and Richard B. Hallick, "Changes in the Expression of the Chloroplast Genome of Euglena gracilis during Chloroplast Development"" Biochemistry 15, 593-599 (1976). Richard B. Hallick and Carol Lipper, "Selective Transcription of the Euglena gracilis Chloroplast Chromosome in Vitro, " ICN-UCLA Symposia on Molecular and Cell Biology, Vol. 5, 1976. Academic Press. In press.